It is desirable to be able to detect and measure ionizing radiation in various instances. For example, space and air vehicles may desire to detect and measure radiation to assist, for example, in the avoidance of radiation exposure. Additionally, terrestrial applications, such as various security applications, may desire to detect and measure radiation, either to assist in the avoidance of radiation exposure or otherwise.
Geiger counters are conventionally utilized to detect and measure radiation. While functional, Geiger counters may be relatively expensive which may curtail their widespread use. In addition, Geiger counters may be considered relatively sizeable with their size also serving to limit the applications that may be effectively served by Geiger counters.
RADiation-sensitive Field Effect Transistors (RADFETs) have also been developed to detect radiation. A RADFET is a p-channel enhancement metal oxide semiconductor field effect transistor (MOSFET) that is specifically designed to respond to doses of ionizing radiation. Further details regarding RADFETs are provided, for example, by Holmes-Siedle, Ravotti and Glazer, “The Dosimetric Performance Of Radfets In Radiation Test Beams”, IEEE Nuclear and Space Radiation Effects Data Workshop, July 2007. RADFETs generally have a relatively large starting voltage. Upon exposure to radiation, the output of a RADFET shifts or alters from the relatively large starting voltage by a relatively small amount. In an effort to facilitate the measurement of the amount by which the output of a RADFET has shifted and, in turn, the amount of radiation to which the RADFET was exposed, the output of a RADFET may be amplified. The amplified output is limited, however, to a value no greater than the supply voltage utilized for the amplifier. Since the amplification of the output of the RADFET amplifies not only the change in the RADFET's output that is occasioned as a result of the exposure to radiation, but also relatively large starting voltage, the output of a RADFET may not be amplified as much as desired in some applications.
As a result of the relatively small change in the output of a RADFET upon the exposure to radiation and the limitations upon the amplification of the change, the sensitivity with which RADFETs may detect incident radiation may be somewhat limited and, at least for some applications, may be less than desired. The relatively small magnitude of the change in the output of a RADFET in response to the exposure to radiation may also require relatively complex detection and measurement circuitry to be required in order to detect changes in the output of a RADFET in response to exposure to radiation. This detection and measurement circuitry may disadvantageously increase the cost of a dosimeter that relies upon RADFET technology.
It may therefore be desirable to develop an improved dosimeter that may have a relatively small form factor and may be more economical, while offering improved sensitivity relative to at least some of the existing dosimeters.